<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>监听</title>
    <script src="../../UI/vue/vue.js"></script>
</head>

<body>
    <div id="root">

        <h2>今天天气{{info}}</h2>
        <button @click="change">切换天气</button>

    </div>
    <script>
        Vue.config.productionTip = false //阻止 vue 在启动时生成生产提示。
        const vm = new Vue({
            el: '#root',
            data: {
                isHot: true,
            },
            computed: {
                info() {
                    return this.isHot ? '炎热' : '凉爽'
                }
            },
            methods: {
                change() {
                    this.isHot = !this.isHot
                }
            },
            watch: {
                isHot:{
                    immediate:true, //初始化时让handler调用一下
                     handler(newValue,old){
                        console.log('isHot被修改了',newValue,old);
                }
                }
            }
        })
    </script>
</body>

</html>